Bleeding your car brakes removes the air from its lines, ensuring proper functionality. This is necessary to ensure your brakes function correctly. In this guide, I will help you understand whether you should bleed brakes with the car running.
So, do you bleed brakes with the car running? You do not necessarily have to bleed brakes with your car running. If you intend to remove the air from the system, bleed the brakes with your vehicle off. To do this, apply and release the brake pedal multiple times until the system removes all the clearances. You will notice an improvement in how the brake pedal feels, but generally, the brake should be as firm as before the bleeding process.
Whether you bleed your brakes while your car is running or not, be careful or hire a professional, as a slight mistake could damage your brake system. Regarding bleeding your car brakes, a major concern is whether your car should be on, and I will respond to this concern in the section below.
It is not advisable to bleed your brakes with the car running. A running engine will supply a vacuum boost to the system, which is unnecessary. Hence, turning off your car when bleeding brakes is appropriate. To bleed your brakes, apply and release the brake pedal until the system takes all the clearances. Eventually, your brakes will be firmer than they were before the process.
While you do not necessarily have to turn your car on during bleeding, this decision depends on your car model and type. A vehicle requiring manual bleeding does not need to be on. On the other hand, newer car models will require you to turn on the ignition but not run as they can use a scanner given their electric parking brake and ABS module.
With your car off, the only pump running during the bleeding will be the ABS. If you are bleeding the ABS, you will need the pump to run; if bleeding the base brakes, you do not need the pump. As you press the brake pedal, the brake fluid will work as your leg moves the plunger in the master cylinder that pumps the brake fluid through the brake lines. This fluid exerts pressure on the brake pads, squeezing your vehicle’s brake disks.
As stated earlier, you do not need your car on when bleeding your brakes as without any vacuum assist, a 7/8-inch cylinder, for instance, under heavy braking, will develop up to 167 pounds per square inch of pressure.
Such pressure, acting on the wheel pistons, can stop a racing car at high speed. You do not need such pressure to bleed your brakes and eventually slow down. As such, the brake fluid is an important component of the brake system and can work well for years without replacement.
Over time, the brake fluid will start losing its moisture resistance. This causes it to absorb water gradually, reducing its performance. Water absorption can also corrode parts of your brake system. For this reason, replacing your brake fluid at recommended intervals is advisable. Bleeding your brakes enables you to achieve this, and with handy tools, you can achieve this with an assistant.
Bleeding your brakes prevents air from replacing your brake fluid. During this process, you will push air against the open bleeder screw. This process needs more than three pounds per square inch and not more than 100. Using higher than recommended pressure can create problems by blowing the lid from your collector bottle or the tube from the bleeder screw.
Also, running your car engine will not increase your brake line pressures as the running engine lacks a mechanical connection to your brake system. While the brake booster uses the engine in operating its diaphragm, it does not increase the brake line pressure.
The only function of the brake booster is to reduce the pedal pressure necessary in the master cylinder operation. This said, an adult can apply the required to bleed their brakes without running the car engine.
Whether you bleed your car while running or not, you should be cautious of some factors that could block successful bleeding. This includes bleeding the master cylinder and the brakes at each wheel. Ideally, a dry or new master cylinder requires bleeding.
Since the brake fluid is hygroscopic, it will absorb moisture from the air, which is bad for the system. To bleed your master cylinder, have a helper press and hold your pedal without pumping. Next, crack or loosen one of the brake lines at the master cylinder, then tighten the line. Your helper can then lift off their foot from the pedal.
Repeat this process until a solid fluid comes from the master cylinder lines. You should never let your master cylinder run out of fluid, as this will flip the cup seals and damage them, necessitating a new start of the bleeding process.
Each vehicle’s bleeding sequence depends on the distance between the master cylinder and bleeding screws. The sequence starts from the right to the left rear, then from the right to the left front. You can gravity bleed your brakes if you do not have a helper. Alternatively, have a helper hold down the brake pedal as you bleed your brakes on every wheel following the bleeding sequence.
Bleeding brakes require you to open the valves to allow the air to escape under pressure. With this release, some brake fluid will also escape. Given the location of the valves in your car, I will help you know whether achieving this process requires you to remove your wheels.
You can bleed your brakes without removing the wheels if you do not mind crawling under the car to access the bleeder nuts. To do this, you should lift your vehicle with a jack to easily access the screws. Some car owners prefer to remove their tires, but this can be extra work. Either way, you will need a helper to assist you on the brake pedal as you get under your car.
Bleeding brakes without removing wheels is technical, especially for first timers. It is advisable to learn it from someone else before attempting for the first time to clear your doubts. However, if you are a handy person, you can navigate through the steps with a few instructions.
Successful bleeding without removing the wheels requires you to start by buying a replacement brake fluid. Depending on your car, get the correct fluid and the intervals you need to replace it. This is given that different car models have different requirements and working with your car’s requirements is ideal. Consult your car manual for the specific brake fluid and the intervals specified by the manufacturer. You should also pick the right quality of the brake fluid. Brake fluids are affordable; in most cases, you will need up to three of the 12-ounce cans for your brake system.
With the right fluid, raise your vehicle from the ground, on the driveway or garage floor, and support it with jack stands at the jacking points as stated in your owner’s manual. A cinder block can work in place of a jack stand, but you should ensure your car is stable enough to prevent it from falling as you work on it.
Next, locate the four calipers on your vehicle and loosen the bleeding screws on them. If the screws have rust, hence not loosening quickly, lubricate them with an oil spray, leave for a moment, then try again. If you still have difficulty opening your screws, consult a professional for help.
The next step will be to check the Cylinder Reservoir for fluid levels. To do this, lift your car hood, and if the fluid is below the line marked full, you will need a top-up. Starting from one brake, insert one end of the tube over the bleeder screw and the other in a container.
Ask your assistant in the car to pump the brake pedal and alert you when they achieve a firm pedal and should maintain the pedal. While you maintain the pressure, open the bleeder screw slightly. This action will cause the pedal to drop as the fluid flows through the tube. Your helper should alert you before the pedal drops completely so you can close the bleeder screw and then repeat the bleed process.
Once you bleed all four brakes, observe the fluid motion in the cylinder reservoir. Repeat the bleeding process if there is a significant fluid eruption, then tightly screw the bleeder screws in place.
With proper bleeding, you will prevent your car from further damage. This saves you the repair and replacement costs. The air in the brakes lowers the car’s braking system. Hence, with proper bleeding, you will also improve your braking system performance, improving your fuel economy.
A common concern among car owners is whether leaving their emergency brakes on while bleeding the front brakes can affect the bleeding process. I will help you know whether you can bleed with the emergency brakes on and the implications.
You can bleed your brakes with the emergency brakes, and the system will bleed similarly to when you apply or release the parking brake. Some users, however, claim to experience a spongy brake pedal, especially with the air in the system after this bleeding.
Bleeding your brakes with the emergency brake on should not be an issue as these brakes are mechanical, and their control is through the cable connected to a foot pedal. On the other hand, the primary brakes are hydraulic, requiring occasional replacement due to oxidation. As such, the emergency brake lacks bearing on the hydraulic brake operations.
Most car brakes are hydraulic, and if air finds its way into this system from a leak or improper bleed, the force from the brake pedals will compress the air. This means that the energy you exert on your brakes will not transfer to the brakes as it should, necessitating bleeding. During bleeding, you need handy tools such as the hose.
You can bleed without the hose, though hoses make the process convenient. Without the hose, you will use the traditional method, necessitating a second party to help you with the job. The second party will be in the car to operate the brake pedal. Their role will be to build pressure on the brakes while you will open the bleeder screw on the calipers.
As your helper pumps the brakes, go to the farthest caliper and have them press the pedal a few times. Next, ask them to push the pedal down and as they do so, open the bleed screw to allow the air and fluid out.
To catch the fluid, you can use a paper cup. Ensure you close the bleeder before the second party lets off the pedal, lest you pull air back in. Your helper should also put their other foot below the pedal to avoid pressing it against the floor.
The hose blocks air from getting into the system as you drain excess Brake Fluid off the system during bleeding. Given the system design, bleeding is possible with improvised options such as a can, but you should be ready with the mess. Either way, work on the four calipers starting with the farthest. It may take a few pumps on each caliper before you successfully clear the fluid, and you have to be patient.
Bleeding your brakes saves fuel efficiency and improves your brake performance by removing trapped air from the system. You can bleed your brakes with your car off, as a running engine will supply an unnecessary vacuum boost to the system.
With your car off, apply and release the brake until the system takes all the clearances. You can also bleed your brakes with the emergency ones on as they are mechanical, bearing little to no effect on the hydraulic ones.
Removing wheels during bleeding is unnecessary as long as you can access the calipers. To improve efficiency, lift your car with a jack and perform the bleeding with the help of a second party. Finally, while the hose is an essential tool during bleeding, it is not mandatory, and you can use the traditional method as long as you do not mind the mess in the brake fluid spillage.